For every action, there is an equal and opposite reaction. So said Newton in his third law of motion. I believe it, though not exactly in the same way good ol' Isaac probably meant it in the strictest physics sense. Action:I had the chance to sneak away from the Lawrence office before darkness descended yesterday, and with the weather unseasonably warm (it had dropped into the upper 50s by then) and the winds generally calm, I hit the river levee for a run. Things felt good, so I pushed it for a five miler as an out-and-back on the flat course.I don't have the records to prove it, but I think it was the fastest 5-mile run in at least five years, if not ever. O_O The only comparable run in terms of pace that I can access hard data from, is a 3-mile run on the same course in August where my pace was only :17 faster.Reaction:The reaction started about three hours later when the aliens wriggled under the skin of my baby cows and started to crawl. I had muscle spasms leading to cramps until the mid single digits of the morning. Not a lot of fun. As I lay in bed, about to drift off, the spasms would detect my complacency and explode into a full-on cramp. The only thing to do was to leap out of bed and slam my heel to the floor and stretch that bad boy. That sucked. I think the aliens finally gave up between one and two in the morning.The reaction makes me wonder if the action of a fast time run was worth it. Below is a camera-phone video capture of the spasms. As I said, they later did get worse and morph into cramps, but I didn't feel like whipping out the camera whilst writhing in pain in the dark of night.